Bomb sight and pilot director



Jan. 11, 1938. I H. s. meu 2,105,147

BQMB SIGHT 58D PILOT DIRECTdR Original Filed Feb. 8, 1960 11 Sheets-Sheet 1 1 INVENTOR Jan. 11, 1938.; H; B. INGLIS l BOMB SIGHT AND PILOT DIRECTOR 11 Sheets-Sheet 2 original Filed Feb. 8, 1950 Jan. 11, 1938. H. B. INGLIS ,1

BOMB SIGHT AND PILOT DIRECTOR Original Filed Feb. 8, 1930 ll Sheets-Sheet 5 //.1 1 S T //7, ,1 a

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H6. 7 1076' 6 INVENTOR A E). LQQQ Jan. 11, 1938. H. s. meus 2,105,147

v I BOMB SIGHT AND PILO T DIRECTOR Original Filed Feb 8, 1930 11 Sheets-Sheet 4 v In /46 21 0 zqa 2 45 6 INVENTOR FIG. 50

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1 Jim. 11, 1938. H. 8. 116115. 2,105,147

BOMB SIGHT AND PILOT DIRECTOR Original Filed Feb. 8, 1950 ll Sheets-Sheet 5 INVENTOR Jan. 11, 1938. H. B. meus I 2,105,147

BOMB SIGHT AND PILOT DIRECTOR Original Filed Feb. 8, 1930 ll Sheets-Sheet 6 INVENTOR misx u Jan. 11,1938, I H. B. us 47 I BOMB SIHT AND PILOT DIRECTOR I ori ina; F-ild Feb. 8, 1930 11 Sheets-Sheet 7 IIIIIIIIII;

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I BOMB SIGHT ANDPILOT DIRECTOR Original Filed Feb. 8, 1930 ll Sheets-Sheet 9 l1, H. B. msus I 2,105,147

' BOMB SIGHT AND P ILOT DIRECTOR Original Filed Feb. 8, 1930 ll Sheets-Sheet 1O H. B. INGLIS BOMB SIGH'IVAND PILOT DIRECTOR Jan. 11, 1 93 Original Filed Feb. 8, 1930 ll Sheets-Sheet 11 INVENTOR m w F 7 MR wR MR R N Rn Patented Jan. 11, 193

BOMB SIGHT AND mo'r nnmc'roa Henry B. Inglis, Flint, Mich.

Application February a, 1930, was... 426,808

Renewed June 15, 1986 "ac (01.33465) My invention relates to?" the "general class of computing mechanisms and ,more' specifically,

mechanisms in combination with"a process of sighting by optical means, for computing data for the aiming of projectiles. The present invention also comprises improved instrumental means for the guidance of the pilot of craft, particularly aircraft. In this class of apparatus are instruments called bomb sights devised to enable the operator or bomber to determine, during the flight of a carrier aircraft along the course at a certain altitude above the level of the objective, when to release a bomb, or bombs, corresponding to the arrival'of the craft where it is distant from the objective, the horizontal component, or range, of the bomb trajectory which the bomb, after release at that position, will thereafter follow.

The principal advantage of my invention over devices of this kind heretofore employed lies in the. fact that it does not require continuous manual manipulation and attention except when corrections arenecessary, in contrast to the conditions heretofore obtained in operating these devices wherein an operator was obliged to actuate,

the controlling elements continuously. I thus avoid the personal errors which enter into the operation of range finders of the type heretofore employed. f

Another object of my invention is to provide a. mechanism that is greatly simplified over that heretofore employed. One of the means which I employ to obtain this result is such a construction wherein a singlefactor is mechanically introduced into several different settings simultaneously and by a single operation. Thus, for example, a single setting of altitude-is entered into the mechanism for synchronous training of line of sight for establishing range as a function rOf altitude and in the trail correction to obtain summital speed. Another method by which I obtain this result is by providing a mechanism wherein only four factors need be set, namely, synchronizing the line of sight into visual coincidence'with the objective, altitude, air speed, and type of bomb, and wherein the last three of these factors may be prc-set with precision and the first be pre-set approximately, and any of them may be re-set any time up to the instant for bomb release.

A further object of my invention isto obtain a quicker and moreaccurate setting of range by utilizing the principle that the range angle is o a function of the usual altitude factor and of the novel factor of summital speed, which I define as 'an'ge dividedbythe time of fall in vacuum true a. ballistic 'co rrectiori.,j 1

It is a further object of my invention to provide a novel azimuth directing system whereby the course of the craftand the vertical plane of the reticule may be quickly and effectively brought into coincidence in the plane of the target. For this purpose I provide means for changing the course of the craft and for changing aircraft, with relations between its horizontal travel and the objective.

, Fig. 2 illustrates in plan view of Fig. 1, relations vertical plane, the trajectory of a bomb released from orfground speed "(or speed of approach) minus between the crafts direction of horizontal flight and the bombing approach.

Fig. 3 illustrates an optical field of view through directional and range reticules. 1 i

Fig. 4, shows in perspective, thetrajectory of a bomb in vector relations to an aircrafts cross wind course.

Fig. 5 is a plan view of Fig. 4.

Fig. 6 illustrates the. elements of a bombsight constituting a line of sight at the range angle.

Fig. 7 shows the elements of the range setting mechanism.

Fig. 8 isa schematic diagram showing the interrelations between essential mechanisms of the bombsight proper.

Figs. 9 and 10 are geometric illustrations of th principle of operation of the correction unit. 1

Fig. 11 is a sectionallzed side elevation, showing the elements of the stabilized optical system.

Fig. 12 is a plan view showing universal suspension of the-gyroscope stabilizer of Fig. 11.

Fig. 13 illustrates from the bombers eye view,

relations between the stabilized reticule references, and the unstabilized field of view.

Fig. 14 is a diagram in side elevation of a vertical plane, showing further relations between the objective and the use of the sighting reticules.

Figs. 15 and 16 illustrate relations between the stabilized directional reference reticule, and alignment of the craft's course in azimuth, relative to the objective.

Fig. 17 illustrates an improvement in the use of a stabilized range reticule.

Fig. 18 shows in side elevation, detail means of indicating the craft's relation in range to the instant for bomb release, and of actuating automatic bomb release and for hand release lead.

Fig. 19 is an electrical diagram of the operation of Fig: 18. I

Figs. 20, 21, are plan and partially sectionalized side views, respectively, of one form of the level detector device.

Fig..22 is a perspective view of another form of the level detector device.

Figs. 23, 24, are plan and side elevations of one form of gyroscope caging and uncaging mechanism.

Fig. 25 is an electrical diagram showing the operation of the level detector device, and features of improvement in the application of gyroscope caging' and .uncaging.

Figs. 26, 27, are side and plan views of a limit device, detail of Fig. 25.

Figs. 28, 29, are a sectionalized plan view and side elevation showing protective features in the application of a gyroscope.

Fig. 30 shows in perspective, a further feature of protection of gyroscopes and reticule, relative to assembly in the instrument.

Fig. 31 is a fractional sectional view taken on the line 3l3l of Fig. 28, showing a further protective device.

Fig. 32 is a side elevation, sectionalized along 32-32, Fig. 33, of all range mechanism shown diagrammatically in Fig. 8, except that of the correction'unit, and of details which, for clarity, are separately shown in other figures.

Fig. 33 is a plan view, sectionalized along 33-33, of Fig. 32.

Fig. 34 is a perspective illustration of a tumbler gear shift, for transmission reversal.

Fig. 35 shows a suitable form of the limit slip clutch.

Fig. 36 shows in side elevation, the disc-balldrum variable speed transmission, with details of a suitable ball carrier.

Fig. 37 is a plan view of the ball carrier of Fi 36.

Fig. 38 is a plan view of the instrument, and Fig. 39 a side elevation sectionalized along 39-39 of Fig. 38, showing all dial sets mechanism, with exception of the speed correction unit (which is sufficiently clear from Fig. 8).

Fig. 40 is a plan diagram showing how the course of an aircraft is aligned on a stationary bombing objective by the pilot directing system.

Fig. 41 illustrates the three cases of directional misalignment for which the pilot directing system is selectively adapted; also alignment relations to fixed and moving targets. n,

Fig. 42 illustrates how the pilot directing systemfapplies' to alignment on a moving objective.

Fig. 43 is a wiring diagram of the electrical part of the directional control.

Figs. 44, 45, 46, are respectively left side elevation, plan view and face view of the pilots indicating instrument.

Fig. 47 is a wiring diagram of the pilot di-a rector.

Fig. 48 is a face view of the directional control, omitting the frame.

Fig. 49 is a left side view of the assembled control showing a frame in section.

Fig. 50 shows separate face view of the three ratio change gear and cam combinations of Fig. 49.

Referring to the drawings, my bombsight is devised to enable the operator, or bomber", to determine, during the flight of a carrier aircraft along a course, as XRC (Fig. 1), and at an altitude", as V x, above the level of an objective,

T, when to release a bomb, or bombs, corresponding to the arrival of the craft, as at R, where it is distant from the objective, the horizontal component "range, TV, oi. the bomb trajectory RB'I', which the bomb after release at that position, will thereafter follow.

This. trajectory range is accurately calculatable from ballistic data according to the specific combination existing at the instant the bomb is released, of four flight variables; "altitude" of craft above the level of the objective; speed oi craftrelative to the objective, called "ground speed" with reference to a stationary objective, or "relative speed of approach in case of a moving objective; speed of craft relative to the air, called air speed; and type of bomb, or its corresponding coefllcient of friction commonly expressed in "terminal velocity. The range may vary by hundreds and thousands of feet, between one bombing approach and the next, according to the combination of those flight variables, and it isa composite'and not simple function of their values. Thus, while it is the common primary function of all types of bombsights to pre-set'a line of sight, as XY, RT, at the range angle (symbol a) with reference to vertical, V X, VR, so as to subtend at the obiective's level, the bombs range, or, to indicate when the craft reaches the position, as R, corresponding to intersection with the objective of a line of sight between instrument and objective at the predetermined angle a with the vertical, there are many diverse principles and mechanical applications for accomplishing this, varying all the way from rough approximations or dependence in part have been. devised upon sui'ficiently accurate bases of applying the basic range formula, none have produced at high altitudes and under ordinary conditions not favorable to care and deliberation in. operation, the degree of precision,

measured by average results, which it is the obiect of my invention to insure. v

While I claim no great betterment of purely instrumental precision over that of certain types of instruments heretofore known using the ballistic formula in diiferent manner, it will become clear from-the description that I have devised a system of-mechanisms and manipulation having novel features to obtain thefullest advantage of the high order of instrumental precision of which the principle is capable. This is accomplished largely by greatly reducing the chances for entering personal errors in the process, by rendering the mode of manipulation of the utmost simplicity, and by insuring reliability of operation.

Some features of my inventions may be adapted to othenuses; as for aerial photography, antiaircraft computers, or navigational use. I shall, however describe them as embodied in a complete bdmbsight for rendering aerial bombing a formidable military weapon of offense.

i While bombsights differ widely as to methods employed in applying the basic range formula and in'correcting for air resistance effects upon the bombs trajectory, i. e., as to methods of introducing the values of the four flightvariables,

thethreefactors.altitude, air speed, and typeof bombareknown in flight, whereas ground speed must be determined during the bombing approach and be combined with the other three factors to determine true range angle or instant ofbomb release in range. Bombsights may, therefore, be separated into three distinct categories according as they may be based upon one of three general principlesfor determining ground speed,'viz.,

' -drift", "tlming, ,"synchronousfl involving essentially different mechanical applications and each category comprising several different and novel means. i I

"Drift methods maybe said to include all the various means for determination of ground speed as the vector resultant of "wind and the crafts air speed. Drift methods involve such prescribed manoeuvering of the flight course as is :rarely practicable under wartime handicaps against holding prescribed straight line flight for more than a few seconds time, hence they are usually short cut, in "practice, by estimation of wind and the entering of a correspondingly inaccurate ground speed value, and are limited to rather low altitudes or to such favorable conditions as do not, on the average, obtain."

Timing methods, may be said to include all means for determining ground speed as an average, over some time interval of measurement. They differ, as by timing over a distance, time, or angle, which may be a constant, or varying according to altitude. Timing methods are capable of accuracy on the condltion that the speed of approach remains constant during the time. of measurement and up to the instant of bomb release, but under average actual conditions, they involve considerable instrumental inaccuracies, require exacting attention, and allow large person- 8,} errors of timed actions in the process, all resulting in an excessive proportion of wild shots and a large average error.

fSynchronous" methods may be said to include all means for determining ground speed as an instantaneous rate, not involving any specific timinginterval of measurement. My invention comprises a synchronous method, differing from other synchronous methods in mechanism, mode of operation, basis of approximation of the basic ballistic range formula, and mode of introducing air resistance corrections.

It is necessary to an understanding of any bombsight, and, of the advantages of. my inventions over the present state of the art, to considenbriefly the nature of a bombs trajectory and} ,the directional vector relations between wind, airspeed, and ground speed.

A bomb, like a gun projectile, follows the wellknown] law of falling bodies. The specific trajectory orpath RT (Fig. 1) of a bomb, and the range VT, of thatpath, are accurately determinable by ballistic calculations for any given combination of the four flight variables; altitude, VR, of the craft, R, above the level of the objective, T; air speed and ground speed of the craft at R, along course XR; and type of bomb. For the sake of clarity, consider for the moment Fig. 1 to illustrate the case ,of no wind, in which case the crafts speed and direction through air and over the ground are the same, i. e., its course RA reference to air is the same as its course RG reference to the ground. The bomb, released from the craft at. R, takes on, due to gravity, a vertical component speed, parallel to RV, accelerating almost uniformly, but by virtue of the momentum and horizontal speedwhich the bomb possesses in common with the craft when released at R,

the bomb continues, concurrent with increase of vertical component speed, to travel ahead at the initial horizontal component speed, exceptas this is graduallydiminished by air resistance, with the net result that the bombs actual path RBI, in air, is a modification of the strictly parabolic path, RUF, which it wouldrollow in the same time of fall in avacuum. a a a Y Fig. 1 is theside elevation of a vertical plane XAEV through the course of the craft RG over the ground, and assuming for this figure no-wind, the course of the craft through the air coincides with its course over the ground and both the vacuum path RUF, and actual path RBT, would lie in this vertical plane. Fig. 4 will be described later, having to do with directional corrections of the crafts course, RG, which is not in line with the crafts heading RA through the air, but is the vector resultant of RA and the cross wind AG. Referring again to Fig. 1, and Fig. 2, (plan view of Fig. 1) it will be seen that the problem of directing of the craft by signalling its pilot, is to align the vertical plane RCTV of the crafts course XRG in which plane the bomb path RBT will lie, to intersect the objective T by the time the craft shall have reached R, the range distance away, and not toleft as XRP or to right as X"RS. Having established correctalignment, XRT, as at X, the function of the bonibsight proper is then to determine the arrival of the craft at R, when it isdistant from the objective, the correct range, TV, of the bombs trajectm'a.

, Means for accomplishing the first function of directional alignment of the crafts course in azimuth, may, or may not be incorporated with the bombsight proper. These two functions are essentially separate in that alignment is accomplished by the pilots control of the craft in accord with signals to turn and. the alignment is maintained until the bomb is released, at R,

whereas range VT, or arrival of craft at R, in

range, is determined solely by the bombers use of the bombsight proper, conditioned on such prealignment of the course and ofthe plane in which the bomb will fall. At high altitudes, however, accurate alignment of the course involves an accurate stabilized directional plane of sighting, RGEV, Fig. 1, Fig. 3, such as the pilot cannot use. Since the bombers cross sight, i1..tn, Fig.

3, for sighting the objective with reference to strictly horizontal at release; craft oscillations.

imparted to the bomb at release; changes of wind and hence, of the bomb: air speed during its fall. The actual'deviation of the bomb from its type trajectory, resulting'irom all of these sources, i s known as to average degree for a given type of bomb, type ofsuspension, and altitude, but-is indeterminate asrto degree or direction in advance, for anyone shot, hence, permits of nocorrection and is independent of skill or instrument This, average error is, however, so small that it would not alone materially detract from highly effective bombing against any but the smallest area objectives, even 'from great heights. The real problem of accuracy is, to reduce the far greater errors which have occurred on the average from the inherent instrumental inaccuracies, from sources of personal errors which the modes of operation heretofore used have permitted, and from short-comings in stabilization.

In Fig. 1, the horizontal ground lag, UT, of the bomb behind its vacuum trajectory, is due solely to air resistance, and this lag (symbol G1.) is a composite known ballistic function of the variables Altitude (symbol H) Air speed (symbol S.) Type of bomb (symbol T. V.)

But the bomb lags against its direction of motion RBT, through the air. Hence, it notonly lags by the ground lag UT in horizontal component direction, but also in a vertical component direction, i. e., it lags, as, by, "I'B, back of and above the corresponding vacuum position, U. In the time of fall (symbol Tv) of the bomb in a vacuum, to reach U from R, the bomb on its air path is at such position as B, hence the actual time of fall from R to T is (Tv+TL). This time lag" (symbol T1.) is another composite known ballistic function of the same variables H, 5,, T. V., which determine ground lag. I 7

During this time lag, the theoreticalvacuum path would extend from U to F, a horizontal ground component UE, which may be called time lag distance, and UE=S9XTL where S; is the symbol for ground speed.

Hence the trail, ET, of the bomb hit, T, back of the ground projection E of the bombs corresponding position F in the vacuum path, is

Trail, ET=UT+EU=GL+ (SgX TL) Now, VE, range of the vacuum path in the actual time of fall, is simply the bombs initial horizontal ground speed Sg at release with which the bomb in vacuum continues to travel forward without retardation, multiplied by the actual time of fall (Tv+TL) i. e.,

and the true range, VT is this distance VE, mi s gal. E 1- 1 (1) True range,

which is the well-known ballistic expression of true range in terms of factors-which are all (112- terminable from ballistic data on bombs, in terms of the four flight variables.

' It is evident that the true "range angle (symbol a) at which the line of sight, XY, Fig. 1, must be set ahead of true vertical XV in order to subtend the range, is

True Range Now, S. is determined by my synchronous system, as I will show.

Tv is a known function of H only TL is a known function of 8., T. V., H I G1. is a known function of 8-, T. V., H

S- is read in flight of! any well-known air speed indicator carried on the craft.

' H is altitude of craft above the level of the obiective; i. e., height of craft above sea level minus height of objective above sea level; the latter is usually known before the bombing mission; height of craft above sea level is read off any calibrated altimeter carried in the craft, hence I will call H hereafter. altimethod for determining S first consider thevacuum path RU, Fig. l, as if there were no air resistance. There would then be no ground lag UT (symbol 61.), no time lag (symbol TL) and no correction forair speed (symbol S.) and Formula 1 becomes (3) Range (i -vacuum) VU(F 'ig. 1) =sq X To Now, actual range VT, Fig. 1, departs from vacuum range VU, by the distance UT, a correction which is small relative to the whole range, though here shown exaggerated for clarity of illustration, hence we may first consider the fundamental bases of different sighting mechanisms in terms of vacuum range, 1. e., in terms of S and H only, and then, the method of correcting for UT.

. First based upon the vacuum range, the elements of any bomb'sight may be considered to be a line of sight rt, Fig. 6, (corresponding to a straight line drawn from R to U, Fig. 1, (instead of RT) formed by eye alignment with two pins 1' and t, adjustable respectively along a vertical leg rv and a horizontal leg vt, at right angles to each other, or, any equivalent optical line of sight as r-t, axis of a telescope (Fig. 3).

Now, if spacing vt be laid off to any scale proportional to the vacuum range, distance VU, Fig. 1, while 10 is, to the same scale, spaced proportional to the altitude VR, also a distance, then tan vacuum range angle= and the line oi sight rt will thus be positioned to subtend the vacuum range, and the intersection of this line of sight with the objective (U, in case of vacuum) indicates instant for bomb release.

Again, if vt be spaced proportional to the bombs horizontal component summital speed range (equal to T,

while or be spaced to thesarne scale proportional to the bombs vertical component summital speed zf range 1! range S, T, (4) n T, 1, altitude. H i i. e., the same angle a is established by spacing both vt and rv either to corresponding component distances, range and altitude or, to correspondinghorizontal and vertical, trajectory component,

summital speeds. g

Under the latter principle of spacings are many possible combinations, such as the following:-

Calibrate a Calibrate m Th at proportional to proportional to "5 1 1 S XT.

F SIXTI I I Do. H S,

a constant HXB (011mm Do.

a SIIXT. s. T.Xa constant a constant Do My system comes under the last elemental category, i. e., I make rv,.Figs. 6 and 7 a constant spacing, while I adjust vt spacing proportional to S, T, X constant H except as I correct for true range angle instead of vacuum range angle, as I will show.

True range VT, Fig. 1, is not SqX Tu, since the bomb in air does not continue throughout its fall, to travel ahead at its initial speed S1, as it would without air resistance to retard it, but this horizontal component speed gradually diminishes. If I divide true range, Formula 1, by Tv, I, will get a "summital equivalent speed (symbol 8,) such that, multiplied by Tv, gives true range, and substituting this S5 for S in the above spacing of vt, thus making at proportional to H I have vr S.XT. (5) tan true range angle, a

I will now describe how, from basic ballistic Formula 1, I obtain by novel trans-positions, ex-

ceedingly close approximations to the advantage of simple application, 1. e., how I obtain a very close approximation to the true value of S. in terms oi the flightvariables; altitude, air speed, ground speed, and type of bomb, and bynovel means of mechanical application, accomplish the quick and simple mode of manipulation which I desire.

In Fig. 7 ED and DF represent the axes, fixed at right angles to each other, of two separately ro- According as these screws are rotated, nuts E and F are displaced to variable spacings ED and FD. A straight axis link, ER, is pivoted on a pin on nut E and is slidably pivoted at a pin in nut F, the pin being slidable in a slot or groove along the link axis. Parallel to ED and at fixed spacing Dv from it, is, the axis of a guide vt along which may slide a member carrying pin t, which is also slidable with reference to the axis of link EFt,-

so that point t is always at the intersection of at and EFt, whatever the spacings ED and DF may be. The four axes ED, ct, D22 and EFt thus constitute a plane geometrical figure such that EDF and tnF are similar right angle triangles in which Now, if I space DE proportional to the before tyn I true range 8. Then triangle. I make rv=K1, and substituting rv for;

Kl, in Equation 8, I have v t true range rv H i. e., vrt is the true range angle when ED and DF are spaced in the above proportions.

Referring to Equation 7, Tv is a known function of H, hence VF T,

Y is a function only of the one factor, H, and I calibrate a scale to which distance DF is spaced by a single setting according to the altitude B, so that Equation 7 is true.

I will now describe how I space DE propor tional to such a summital velocity SS as is substantially equal to It I equate true range to (Sn-51? in which S. is craft's speed of approach, and

tatable screws carrying respectively nuts E and mentioned equivalent horizontal summital veloc- (a. function of altitudeonly) S; is a speed correction to be determined, then the correct value for S1 correction must be we (9) T,

And substituting in Equation 9, the expression for true range, Equation 1,

This is the correct value for S; in terms of the ballistic factors Sa, T1,, 5;, GL, Ty.

Now, To and G1. are different functions of altitude, air speed, and type of bomb andmay be expressed where A, B, A, B are known ballistic iunctions of altitude (H) only, b, b, are known ballistic functions of air speed (SB) only, '0, is a known ballistic function of type of bomb ('1'. V.) only, and substituting the above expressions for T1. and G1. in Equation 10, we have and without changing the value of this equation it may be rewritten 1 (12) S,= (S,.K-S,)X T. X 0

Again, the ratio aim varies chiefly according to altitude, as A, B, and TV are all functions of altitude only. 17 is a function of air speed only, but varies much less than in direct proportion to air speed, and the eifect of b variation upon that ratio is so small for all air speeds within practical'limits, that an average value for b, based upon an assumed average air speed, might be used with small errors in the values of the ratio, but I render such errors still less by calculating the true values of b according to the air speeds which most generally occur at various altitudes, for the type of bombing aircraft in use, and thus I make a single setting for altitude introduce values of this multiplier ratio in exceedingly close correspondence even for combinations of air speeds and altitudes other than normal, and of exact values for normal combinations, so that the range error due to this approximation will average over the whole range of combinations between practical limits, of the order of only about 15 feet, including unlikely combinations.

It will now be seen that Equation 12 expresses the value of the speed correction Sx which I actually introduce, by mechanisms which I shall describe, so that a spacing proportional to S. setting for air speed is first multiplied by a constant K; a spacing proportional to S; is subtracted from 5.11; the spacing proportional to (SaKSg) is then multiplied by a ratio substantially equal t as determined by a single altitude setting; and

chronous process,,and the spacing proportional to the S; correction as above described.

I have now described the elements in principle, of my method of range angle determination, as illustrated by diagram, Fig. 7, comprising the setting of a range arm rt at the range angle 41 ahead of normal vertical axis rv, based upon spacing vt, (at right angles to the fixed legrv) proportional to the product of horizontal summital velocity S! of the bomb, by the vacuum time of fall, Tv, through altitude H, divided by altitude.

H, all by means of locating a link EFt by two spacings DE and DF, so that DE is proportional to the diiIerence between speed of approach S; and the speed correction Sx, and, DF equal to In this mechanical means the only approximation is in the value of the correction Sx, involving small range errors for other than normal combinations of air speed and altitude. I have described the novel developments by which I have re-expressed the true ballistic formula, range=S (Tw+Tz.) -(Gz.+S Tz.) as r a n g e (S -Sx) T I will. now describe the mechanical relation ships of all parts essential to the spacing of DE and DB in the above accord, comprising the means of synchronizing the line of sight into visual coincidence with the objective, and involving but one presetting eachior known altitude, air speed and type of bomb, resulting in the automatic determination of the instant of bomb release.

Schematic diagram, Fig. 8, shows, in the manner familiar to engineers, all essential mechanicalrelations. Description of Fig. 8 may be more clearly visualized by reference to correletters.

In the center of Fig. 8 will be seen, inaddition to like parts of Fig. 7, a pickup arm rI, shown in dotted lines at a random angular position 0, and ahead of the range arm, rt. The mechanism in the center group, Fig. 8, corresponding to Fig. 7, has to do with the setting of the range arm, ft, and nothing to do with the positioning of the pickup arm, rI. Hence, I show the latter in a group, separated for clarity, at the left, including the mechanism which sets it, in full lines, wherein the same range arm, rt, shown in full lines in the center group, is shown dotted and in the angular position a determined by the center group mechanism. Thus, actually, the left group should be superimposed upon the center group in a parallel plane so that the pivotal axis, r, in both groups, coincides.

The group at the extreme right of Fig. 8 may be called the Sxcorrection unit, which will be described later.

It may clarify subsequent description, to dis- .tinguish in Fig. 8, the left group comprising parts driven by motive power II, from the rest of Fig..

8, having to do with settings and not otherwise moved, by tracing the transmission from constant speed source of power II, to the driving of pin 2 nut toward v at any desired constant rate. As H arm bears by pressure of spring, not ,here shown, always against pin 2, rl rotates always as nut 2 is moved along screw 3, and mirror III geared to arm rI, through 5, 6, 8 gears, is rotated in the same direction as arm rI, but, as

will be shown, at half the angular rate.

II represents any suitable source of motive drive of disc III, as electric motor or spring clockwork, having suitable governor device, represented by I2, to maintain disc I3 rotation at a pre determined constant speed, and I4 and I5, worm and gear integral respectively with shafts of the motor, and disc I3, represent any form of transmission ratio to drive disc I3 at the predetermined speed'from motor II, which may have another speed. It will also be understood that any gears in Fig. 8 such as I4 and I5, or 24, 24', merely transmitting rotation of one shaft to another not in the same line, are not essential to the system where the parts may be obviously otherwise disposed, to require more than one set of gears or, to eliminate the gears, the essential 22, and in frictional mesh with the hardened and ground surfaces of both drum I6 and disc I3.

The rate of rotation of I6 and I1 may be changed from zero where idler I8 is pushed to center of disc l3, to maximum speed by shifting idler I8 out to edge of disc I3, and the drive ratio is pro portional to the distance of idler I8 out from disc I3 center. While idler I8. is free to revolve about shaft 22 axis, it is integral with this shaft with respect to displacement of shaft 22 in arrow directions, so that the speed ratio between I3 and I6 is variable by displacement of shaft 22 according to the adjustment for speed of approach by the synchronizing regulator, as will be described later. Similarly, the axis around which drum '23 is rotatable, is at right angles to, and in the plane of, the axis of disc-drum I1I6, and the speed ratio between 23 and I1 is determined by the dis placement of idler 25 in arrow directions, and the ratio is proportional to the distance of the idler out from center of disc I1. This displacement of idler 25 with carrier shaft 34 is according to rotation of cam 32 against which shaft roller 33 always presses by spring, not here shown, through a setting 26 for altitude, which will be described later. A practical means of construction of such disc-ball-drurn transmission is detailedin Figs. 36, 37.

Here, guide shaft 34, pinned at 260 (Fig. 37) integral with ball carrier 26I, is square in section, thus holding carrier 26I (Fig. 36) against rotation. Ball .25 is held accurately located with reference to the carrier by roller 262 pinned in the carrier on that side to which the ball is pressed by the rotation of disc I1; and is held, axially, along a line parallel to the drum23 axis,

against ball 263 in socket 264 of the carrier, by a spring 265 pressing against ball 266. Frictional contact of ball 25 with the disc and drum," may be insured by end play pressure of disc I1 against the ball, by spring 261 (Fig. 36). The same figures may represent also the I3--I8-I6 disc-balk drum transmission, Fig. 8.

suitable gears 24, 24, by drum 23, at a constant speed depending upon the positions of idlers 25 and I8, and rotation of shaft 35 transmits to shaft 44 the same or oppositerotation, according as tumbler-gear-train arm 48 is moved from off position shown (Fig. 34), in which 42 is not driven, to on or reverse" positions, in which gear 42 is meshed respectively with gear 36 integral with shaft 35,- through idlers 38, H or through idler 31. A practical form of this tumbler gear train is detailed in Fig. 34.

Arm 48, integral with gear carrier 39, carries roller 210 bearing by spring 21I against a camway 212 so shaped as to hold arm 40 either at off or on position notches, but requiring 40 to be manualiy held at reverse connection, from which 4|] will spring back to off positionunless held at reverse.

Rotation of shaft 44 in on or reverse tumbler gear connection with motive drive, transmits linear travel of nut 2 respectively toward or away from v, through gear train 45, 46, 41, 48, 49, shaft 54, integral with 49 carrier of differential gears 48,

clutch 43 and screw 3. 41 to 58 represent a wellknown diiferential, in which shaft 54 is rotated as the arithmetic sum or difference of rotations of the differential halves, 41 and 50. Gear 58 constitutes part of a manual setting gear train by which rotation of 54 i'can be added to or subtracted from its rota'tidnby motive drive by shaft 44, but 58 is normally stationary, when screw 3 is then rotated by the motive drive alone, at a constant speed through the half 41 of the differential.

The function of clutch' 43 is to allow rotational slippage between screw 3 and shaft 54 when and only when screw 3 is stopped against rotation, when nut 2 reaches either stop limit of its travel, and when gear 42 is connected to motive drive, in which case motive drive can continue without forcing screw 3 in torsion beyond a slight-frictional twist through the slipping clutch 43. All clutches may be alike,- and a suitable form is detailed in Fig. 35. J

Thus, Fig. 35 may represent clutches I33, 58, I45, Fig. 8, with cranks 81, 25, I23, also clutches I32 and 43, Fig. 8, replacing crank 28 by regulator wheel 93, and omitting the crank for clutch 43. Shaft 28I, Fig. 35, is rotated by turning shaft 282 unless 28I is stopped,.when shaft 282 may then slip in rotation. Members 283 and 284 are pinned to rotate with shaft 282, but slotways 285, 288, allow axial movement of both members along the shaft. Spring 281 compression, forces 284 against one side of flange 288 of shaft 28I, and member 283 against the bottom face of flange 288, so that shafts 28I, 282, are in frictional mesh without any forces along the shaft axes external to the unit.

Rotation of gear 5, integral with pickup arm I, pivoted at r, rotates, through idler 8 pivoted at I, the gear 8 of twice the diameter of 5, hence in the same direction but at half the angular rate. The optical line of sight reflected from the mirror surface I8 makes the same angular movement as the pickup arm I by this well-known gearing of the mirror in the ratio of one to two, hence, in the diagram Fig. 8, 4 may represent theoptical line of sight through the cross reticule which, as will be shown in description of stabilization, is always at the same angle 0 with reference to true vertical that pickup arm TI is with reference to the instrument's normally vertical axis rv, in

other words, considering rv axis as vertical, line of sight 4 parallels arm axis N.

All of Fig. 8 may be considered as a side elevation of the instrument unit holding the plane of the sheet vertical, and while the whole instrument considered integral with the aircraft, be tilted about a horizontal axis normal to the plane of the sheet as by placing 9V vertical, and axis of screw 3 out of horizontal, as in a nosing up of the craft, the optical line of sight through the cross reticule will then be seen as 4, retaining the same angle 0 with respect to true vertical 8V as arm I still bears to instrument axis 10. The angular rate of change of 0 between true vertical V or V and apparent line of sight 4 or 4' through reticule axis T-t, Fig. 3, remains, despite oscillations of the whole instrument with the craft, the same as the angular rate at which pickup arm I is driven with respect to axis rv. Hence, it is not necessary that axis of 3 be disposed horizontally or rv be disposed vertically, as

I here show them to be disposed with respect to I 58, manual rotation of crank 58 will rotate shaft 54 through half of differential 50 and according to the direction of cranking will add such rotation of half of differential 58 to, or subtract it from, whatever rotation half of differential 41 may indicate by tumbler gear connection in one. direction or the other. Hence, the line of sight, or field of view, including the line of sight, may be shifted toward or away from vertical either by connecting motive drive tumbler gears in on or "reverse gear connections without manual rotation of crank 58, or, by manual cranking of 58 alone with motive drive disconnected as shown, or, both, in cumulative or subtractive directions. The advantage of this differential means of shifting the field of view is to enable the bomber to quickly shift the line of sight 4 manually upon the objective which may be ahead of or behind the position 4 as left from a previous approach, to commence synchronizing the rate of movement of 4 in coincidence with the objective, at any angle 0 at which the objective may be picked up by line of sight 4 without changing the speed ratio, nor the rate of movement at which nut 2 will start upon throwing drive on", from that previously established, 1. e., by merely throwing 48 on" soas to drive 2 toward 0 and hence 4 toward vertical, or reverse, so as to drive 4 further ahead of vertical by motive drive till 4 intersects the objective or, if the bomber desires quicker pickup, to add to such constant rate by motive drive, whatever additional speed he desires by hand cranking of 58. Upon intersection of 4 with the objective, the crank 58 is let go and 48 is thrown on" if not already connected, when the line of sight 4 instantly proceeds to .move back at the motive drive rate of nut 2 travel which may have been left established from a preceding approach from the same direction, or as approximately pre-set. The new approach speed may or may not be close to the preceding speed, according as the new approach is or is not nearly in the same direction and with same wind and air speedcombination, but the means for shifting the field of view by hand is of advantage in case the new speed is close to the preceding approach speed by rendering it unnecessary to change the motive drive rate, as would be necessary to shift the angular position of 4 toward vertical in case the objective is picked up behind the previously left position of 4. If the objective lies ahead of the previously left position of 4, then 4 may be shifted ahead by motive drive reverse connection without changing the rate nor cranking 58, or speeded up by also cranking 58, or, by cranking 58 alone,'leaving 42 disconnected until 4 intersects objective when, in any event, H is meshed with 42 by throwing motive drive on.

The hand crank ratio through bevels 55, 55,-

may be any desired ratio to enable nut 2 to be shifted faster than by motive drive, for quick shifting of 4 into coincidence with objective. The motive drive ratio between rate of movement of nut 2 and motor II bears a definite relation to altitude and speed of approach through ratios 13 to 16-17 and 1'7 to 23, such that movement of 2 is directly proportional to speed of approach and inversely proportional to altitude, i. e., actual speed of nut 2 travel is Thus, I displace idler 25 through cam 32, by altitude set 25 by setting calibrated marks of disc against fixed index 52, so that the ratio between speed of rotation of drum "and disc I1 is inversely proportional to altitude and I displace idler I8 so that the ratio of speed of rotation of drum I6 to speed of rotation of disc I3 is directly proportional to the actual speed of approach. When the altitude ratio has been set to known altitude, it only remains to shift idler I8 until line of sight! follows back in synchronized coincidence with or relation to theobjec tive, when nut 2 is then moved at a rate directly proportional to the actual speed of approach, hence the position of idler I9 and corresponding position in rotation of shaft 2| which displaces I8--22 in proportion to rotation in fixed nut bearing 29, of screw I9 against which shaft 22 always presses by spring, not here shown, is a direct measure of the actual speed of approach, and a proportional rotation through worm and gear I95, I94 of disc I9I calibrations,- reading against fixedindex I92, furnishes indication of the speed of approach.

While the range angle a of the range arm rt is thus set, as will be described, inaccord with the synchronous speed of approach without the need ofreading what the speed is, an indication ofspeed of approach has value for navigational information aside from the immediate bombing approach in sight of the objective. The operator of this instrument can determine the crafts groundspeed in a few seconds time by merely setting dial 5| altitude calibrations to index 52,

according to altitude, and then, sighting any ground object along! inthe direction of the crafts ground travel, adjusting 93 till 4 remains coincident with or at fixed space from the sighted object,and reading ,the true ground speed oif dial IIlI.

It will be noted that shaft 2| is rotatable only by rotation of shaft 19, which by other disposition might be a continuation of it or, as through worm wheel I35 integral with shaft and dial I36,

which latter is calibrated to register air speed against index I91, so that rotation of the half 92 of differential and 80, and integral shaft I9, against the frictionally locked setting of differential half 83, corresponds to the displacement ofjidler I8 and to speed ratio between disc I1 1 and drum 23 proportional to the air speed set;

Similarly, if air speed set 91, and hence differential half 82 be left frictionally locked in the position set manually, then manual rotation of the regulator wheel 93 rotates shaft 19 through clutch I32, shaft 92, and gearing 9|, 99, 99, 98, andthus differential half 83 and member 80 and integral shaft 19.

Thus idler I8 could be positioned toproduce the synchronous rate of movement of 4, by rotating either the air speed set or the regulator 93, hence establishment of accurate synchronism of the sight 4 and accurate indication of the speed of approach are not dependent upon setting 81 and dial I36 precisely according to known air speed, but the air speed set 81 serves two purposes for which it should be set according to known air speed before synchronizing by regulator 93. The chief function of the air speed set 81 is that it introduces through transmission gears 65, 84, 69, 68, and differential half 61, the air speedin the factor SBK, which, in combination with the setting of differential half 64 in proportion to S introduces the factor (SaK-Sg) into the Sx correction unit at the right of Fig. 8 through shaft "III. The second function served by the same air speed setting of 81 is, that when differential half 82 is set according to air speed,

then the setting of the regulator 93 to obtain synchronism of sight 4, is directly proportional to the difference between the speed of approach and air speed, i. e., approximately to the wind componentin'line with direction of approach. And dial 96, rotated in proportion toregulator 93 setting, through shaft I99 and worm and gear 98, 99, indicates against index 91, this wind. Thus, by setting 91 for air speed, and also setting upor down-wind speed calibration of dial 96 by 93 set, for estimated up or down wind, the speed ratio I3 to I6 may be thus preset to a resultant rate of drive of nut 2 closely proportional to the actual speed, and but little regulation of 93 is needed to obtain exact synchronism in the shortest time. Also, for navigational use, by flying a ground course up or down wind, ancl'synchronizing 4 on any ground object, dial'96 then registers the true wind velocity.

, Now the position in rotationof shaft I9 is directly proportional to existing ground speed of synchronization upon a stationary ground object, and to the setting of gear II' (half of the right hand differential) through gears 62, 63, also 64 (half of the lower differential). The setting of II proportional to ground speed 3;, in combination with the setting of I4, the other half of the righthand differential through gears I5, 11, shaft I8 and gear I 22 as an output from the S): correction unit, proportional to S: rotates I2 and integral shaft 16 and screw H9 and hence spaces DE in proportion to (Su-S:) factor of Equation 12. How I22 is rotated proportioned to Sx will now be described, referring to Formula 12.-

Air speed, Sa, is to be multiplied by the constant K, and this is mechanically accomplished by makingthe ratio between diameters of gears 68 and 69 equal to K, whence half 61 of the lower differential is, through gears 68, 69, positioned in rotation proportional to 811K- The half' 64 of this differential is, as already traced, positioned in rotation directly proportional to the speed of approach s as soon as sight 4 is synchronized upon the objective, and member 66, integral shaft 19 and screw I96 are positioned in rotation, and hence spacing JL of nut I0! is set, proportional to (SaK-Sg), i

In the speed correction unit right hand group of mechanism, Fig. 8, lettered points refer to intersections of the axes of various parts, projected into the fiat plane of the sheet, though the various parts are actually in parallel planes so that they can pass each other by movements in arrow directions. Thus, while interrelated by pins common to the intersections of overlapping members, links I08 and H6 pivoted respectively at P and R fixed points, are free to separately swing about their pivots; bars I I0 and III are free to move past each other in arrow directions along guides whose axes only are here represented by dbt and 

